Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $248.59   4.864%   $260.6814   $260.68   $260.70   $260.70  
  Purchase #2 $153.86   4.405%   $160.6375   $160.64   $160.65   $160.60  
  Purchase #3 $78.68   5.104%   $82.6958   $82.70   $82.70   $82.70  
  Purchase #4 $210.81   4.786%   $220.8994   $220.90   $220.90   $220.90  
  Purchase #5 $142.75   9.780%   $156.711   $156.71   $156.70   $156.70  
  Purchase #6 $87.92   6.518%   $93.6506   $93.65   $93.65   $93.70  
  Purchase #7 $57.47   7.867%   $61.9912   $61.99   $62.00   $62.00  
  7 purchase totals = $980.08       $1,037.2669   $1,037.27   $1,037.30   $1,037.30